Thermal diffusion method and apparatus



Oct. 423, 19

56 E. N. MARSH 2,767,849

Ph I

*i9 Ph W r 21H mn lz y v l Zi f H C I :QDH f ,///l F *5* f7 24 2/ LM@ l H f6@ M Pc FEV 5 Y/Z m Afb c 1 wf P 1;@ 1% C l 'M @4 P Z0 n P E d V v f fz C CH f-@f+;@f @L/@ l A c C d *Fw-5 lac [own/eq lV/1721275?. PFC- E y BY W Mx', @e 9 am.

United States Patent O THERMAL DIFFUSION METHOD AND APPARATUS Shaker Heights, Ohio, assignor to Company, Cleveland, Ohio, a corpo- Edward N. Marsh, The Standard Oil ration of Ohio This invention relates to an improved continuous liquid thermal diifusion method and apparatus and particular- 1y to improvements in the flow patterns of thermal diffusion methods and apparatus of the types described in U. S. Patents 2,541,070 and 2,541,071 to Jones and Hughes and in U. S. Patent 2,521,112 to Beams.

The Jones and Hughes patents referred to above describe a continuous method for separating, by thermal diffusion, two fractions containing dissimilar materials that are normally liquid under the conditions of separation and which are included in a mixture that is normally liquid under the conditions of separation. The term dissimilar components, as used in the Jones and Hughes patents and in the description of the present invention, is intended to refer to two or more compoents in or of a liquid or liquifiable mixture. These components may be dissolved in a common solvent, they may be liquid components of a mixture or one of the components may be a solvent and another the solute.

The method of the Jones and Hughes patents in essence involves continuously introducing a liquid mixture into apparatus comprising a substantially vertical and narrow separation chamber at a point intermediate the upper and lower ends thereof. The chamber is formed by smooth side Walls, the opposed faces of which are closely and uniformly spaced apart. One of these Walls is relatively heated and the other is relatievly cooled to impose a temperature gradient across the separation chamber or slit formed by these walls and consequently also across the thin film or layer of liquid mixture in the chamber. As a result of the relative heating of the liquid immediately adjacent the hot Wall, a term used in a relative sense, and the relative cooling of the liquid immediately adjacent the cold wall, a term likewise used in a relative sense, two phenomena take place. One of these is the well-known phenomenon of thermal circulation or convection which resolves the liquid in the chamber into two countercurrently moving fractions, one ascending adjacent the hot Wall and the other descending adjacent the cold wall. The other phenomenon, not so well-known, is that of thermal diffusion whereby different amounts of energy of translation are imparted to dissimilar molecules in the mixture with the result that one type of molecule tends to accumulate adjacent the hot wall and the other tends to accumulate adjacent the cold wall. Consequently, the ascending fraction in the charnber becomes relatively concentrated in yone type of dis-v similar molecule and the descending fraction becomes relatively concentrated in the other type or impoverished in the rst type of dissimilar molecules. Withdrawal of a portion of the ascending fraction from the top of the separation chamber and withdrawal of a portion of the descending fraction from the bottom of the separation chamber results in achieving significant separations of dissimilar components in the liquid mixture subjected to thermal diffusion.

In the Beams patent, it is likewise proposed to introduce the liquid mixture continuously into a thermal difv outer ends.

fusion chamber at a point intermediate its ends. The separation chamber, however, is in a horizontal position and the upper wall is relatively heated, Whereas the lower wall is relatively cooled. To supply a means for circulating the liquid in the chamber countercurrently, since this cannot vbe achieved thermally in a horizontal chamber, the patentee proposed to utilize an endless tape moving countercurrently through the chamber and thereby in effect dragging a fraction accumulating adjacent the upper hot wall toward one extremity of the chamber and a fraction accumulating adjacent the lower cold wall toward the opposite end of the chamber for separate removal.

It has now been determined that the methods and apparatus described in these patents have an inherent disadvantage in that the introduction of fresh liquid mixture into the separation chamber disturbs the laminar flow of the liquid fractions at the point of entry and in effect nullies a substantial portion of the separation into dissimilar components that has already taken place in the chamber. Thus, for example, when fresh liquid mixture is introduced into the mid-portion of a vertical separation chamber, it is manifest that the introduced liquid will become intimately admixed with both the ascending and descending fractions and that a zone of turbulence will be established. Since the liquid in this zone of turbulence will consist of a mixture of the fresh entering liquid with the ascending and descending fractions, it follows that the degree to which the ascending fraction has become concentrated in one of the dissimilar components in the course of its ascent from the bottom of the chamber to the inlet and the degree to which the descending fraction has been impoverished in said dissimilar component in the course of its descent from the top of the chamber to the inlet, are substantially completely nulliiied. In effect, therefore, the efficiency of separation ob` tained is determined by the degree to which the fraction ascending from the inlet to the top becomes concentrated in one of the dissimilar components before a portion of said fraction is withdrawn, and the degree to which the fraction descending from the inlet to the bottom of the chamber becomes impoverished in said dissimilar component before a portion of it is withdrawn.

Substantially the same disadvantage is inherent in the moving wall thermal diffusion method proposed in the Beams patent, it being manifest that complete remixing' of any fractions that may have separated would occur at the point of entry of fresh liquid mixture.

The present invention is directed specically to the problem of avoiding the mixing diiculties that are inherent in vertical and horizontal countercurreut ilow thermal diffusion methods and consequently in making the entire length of the separation chamber effective.

ln accordance with the method of the present invention, the countercurrently moving fractions are temporarily separated at the point fresh liquid mixture is introduced into the chamber and, while so separated, one or both fractions are individually admixed with, or one fraction is replaced by the fresh liquid mixture. ln the apparatus of the invention, means are provided, at a location intermediate the outer ends of the separation chamber, for tempararily separating two fractions and for directing fresh Vliquid mixture individually into one or both separated fractions. In eifect, therefore, the separation chamber is divided into two portions, each having inner and One of the countercurrently moving fractions is withdrawn from the inner end of one of the chamber portions and thereby separated from the other fraction. This withdrawn fraction may be admixed with fresh liquid mixture and reintroduced into the separation chamber through the inner end of the other portion in the same direction as the direction of iiow of the withdrawn fraction before withdrawal. in the alternative, the withdrawn fraction may be discarded and replaced by fresh liquid mixture introduced in the maner described. The other fraction may be similarly withdrawn, admixed with liquid mixture and reintroduced; it may be allowed to advance substantially undisturbed from one outer end of the chamber to the other, or it may be withdrawn, discarded and replaced by fresh liquid mixture. 1n substantially all other respects, such as the maintenance of a temperature gradient across the chamber and the withdrawal of dissimilar liquid products from opposite ends of the chamber, the method and apparatus are substantially the same as heretofore proposed.

In the preferred embodiment of the invention, the liquid mixture is confined in a substantially vertical separation chamber because of the inherently greater simplicity of constructions that do not require moving parts. The inlet or inlets and the means for temporarily separating the two fractions and individually directing fresh liquid mixture into one or both the tempararily separated fractions are located intermediate, and preferably midway between, the upper and lower ends. It is not critical to operabi-lity whether the two portions of the chamber etfectively formed by the inlet or inlets and associated means are relatively separate and distinct or whether they are substantially unitary, as will be described more particularly with reference to the drawing forming a part of this application. The width of the separation chamber, i. e., the spacing between the hot and cold walls, should be no greater than about 0.15 inch and preferably between about 0.02 and 0.06 inch.

The primary advantage of the method and apparatus of the present invention is in avoiding nullitication of a substantial portion of the separation that tal-:es place in a portion of the thermal diusion chamber and thereby in increasing the eiciency and yield without any increase in dimensions of the apparatus or in the amount of heat supplied.

This and other advantages, as well as the utility of the invention will become apparent from the following detailed description made with reference to the accompanying drawing wherein:

Figure 1 illustrates schematically one embodiment of the apparatus of the invention;

Figure 2 illustrates schematically another embodiment of the apparatus of the invention;

Figure 3 is a ow diagram illustrating the flow pattern of the apparatus shown in Figure 2 wherein the separated fraction ascending along the hot wall is admixed with fresh liquid mixture;

Figure 4 is a ow diagram similar to Figure 3 wherein the separated fraction descending along the cold wall is admixed with fresh liquid mixture;

Figure 5 is a flow diagram illustrating the ow pattern of the apparatus shown in Figure 1 wherein the separated ascending and descending fractions are individually admixed with fresh liquid mixture;

Figure 6 is a ow diagram similar to Figure 3 but illustrating one embodiment of the method as applied to horizontal countercurrent flow methods wherein mechanical circulating means, such as a moving wall or tape, is utilized.

In all the figures of drawing, the letters C and H are utilized to indicate cold and hot walls of the separation chamber, respectively; P11 and Pc designate the liquid products that have accumulated adjacent the hot and cold walls, respectively, and are withdrawn from the opposite ends of the chamber; the letter F indicates feed of fresh liquid mixture to be subjected to separation by thermal ditusion; and the letter M indicates means for admixing feed with a separated fraction prior to introduction of the feed into the separation chamber.

In Figure 1, a thermal diffusion chamber having upper and lower portions and 11, respectively, is shown as formed by smooth, substantially parallel and vertical walls C and H that are relatively cooled and heated by any suitable means such as coils 0r conduits 12. Inlets 14, outlets 16 and a battle 17 are provided at about the midportion of the separation chamber 10, 11 and outlets 19 and 20 are provided at the upper and lower ends, respectively. The ascending and descending liquid fractions in the chamber are indicated by the upwardly and downwardly pointed arrows.

In operation, `the liquid in the chamber 10, 11 is rcsolved, by virtue of the temperature gradient imposed across it from the hot wall to the cold wall, into two fractions, one fraction being progressively more concentrated in one dissimilar component of the liquid mixture and ascending adjacent the hot wall, and the other fraction being progressively more concentrated in another dissimilar component and descending along the cold wall. At the upper end of the separation chamber a portion of the ascending fraction is withdrawn by way of outlet 19 as liquid product Ph. The fraction descending in the upper portion 10 of the separation chamber along thc cold wall is physically separated from the ascending fraction by the balile means 17, withdrawn from the inner end of the upper portion 10 of the separation chamber by way of outlet 16, admixed with fresh feed in the mixer M and reintroduced by way of inlet 14 into the inner end of the lower portion 11 of the separation chamber to continue its descent along thc cold wall. At the lower end of thc separation chamber, a portion of the descending fraction is withdrawn by way of outlet 20 as liquid product Pc. The fraction ascending along the hot wall in the lower portion 1,1 is separated from the descending fraction by bathe means 17 and withdrawn through outlet 16 from the inner end of the lower portion 11 of the separation chamber. The separated ascending fraction is thereupon mixed with frcsn feed F and reintroduced by way of inlet 14 into the inner end of the upper portion 10 of the separation chamber and directed to ascend along the hot wall thereof.

The apparatus illustrated in Figure 2 substantially similar except for the manner in which the upper and lower portions 10a and 11n, respectively, of the separation chamber are separated. The inner end of the upper portion 10a of the chamber is provided with an inlet 14a communicative with a mixer M, a baille means 17a for separating the ascending and descending fractions indicated by the arrows, and with a conduit 21 that serves as an outlet for the descending fraction and an inlet for introducing said fraction into the inner end of the lower portion 11n of the chamber. The inner end of the lower portion 11a is further provided with a baille means 17b for separating the ascending and descending fractions and an outlet 16a communicating with the mixer M. The upper and lower ends of the chamber 10a, 11a are provided with outlets 19 and 20 for thc withdrawal of liquid products P11 and Pc, respectively. The cold and hot walls C and H are relatively cooled and heated by any suitable means such as the conduits or coils 12.

In operation, the liquid mixture in the separation chamber 10a, 11a is resolved, by virtue of the temperature gradient imposed across it from the hot to the cold wall, into two fractions. One of these becomes concentrated in one of the dissimilar components of thc mixture, accumulates adjacent thc hot wall and asccnds. The other becomes concentrated in another of the dissimilar components, accumulates adiacent the cold wall and descends. The ascending fraction in the lower portion 11a of the chamber is separated from the descending fraction by the baffle means 17h and outlet 16u, admixed with fresh liquid mixture in mixer M and directed into the inner end of the upper portion of the chamber 10a to ascend along the hot wall thereof. TheI descending fraction in upper portion 10a of the chamber iS separated from the ascending fraction by bathe means 17a and transferred substantially undisturbed into the inner end of the lower chamber portion 11a by means of conduit 21. A portion of the ascending fraction is withdrawn as liquid product Ph through outlet 19 at the upper end of the upper portion a and a portion of the descending fraction is withdrawn through outlet 20 as liquid product 1% at the lower end of the lowerV portion 11a.

It is to be understood, of course, that :thefapparatus shown schematically in Figure 1, whereby the fiow pattern of Figure 5 is obtained, can readily be modified to produce any of the flow patterns shown in Figures 3 and 4, and that similarly the apparatus shown schematically in Figure 2, whereby the flow pattern of Figure 3 is obtained, can readily be modified to obtain the flow patterns in Figures 4 and 5. Thus, for example, the fiow pattern of Figure 3 can be obtained with the apparatus of Figure 1 simply by eliminating the inlet 14, outlet 16 and mixer M shown to the left of the thermal diffusion chamber 10, 11 and by removing the horizontal barrier to the left of the banale means 17 so that the descending fraction can advance uninterruptedly fromv the upper portion 10 of the lower portion 11. Similarly, the apparatus illustrated schematically in Figure 2 can be modified to obtain the fiow pattern of Figure 5 simply by interposing a mixing vessel M in the line 21 leading from the inner end of the upper portion 10a tothe inner end of the lower portion 11a.

It is also to be understood that it is within the scope of the invention to discard either of the two countercurrently moving fractions while they are separated and to replace the discarded fraction with fresh liquid mixture instead of admixing fresh liquid mixture with the separated fraction. Furthermore, it is within the scope of the invention to modify and improve the apparatus described in U. S. Patent 2,521,112 to Beams in a manner similar to that illustrated in Figure 1 of the accompanying drawing so as to obtain the flow pattern of Figure 6 or the flow patterns of Figures 4 and 5 turned on their sides.

A determination was made, for comparative purposes, of the results obtainable with four different fiow patterns, all other conditions being equal. Flow pattern A is a vertical, countercurrent fiow pattern in which the feed is introduced into the center of a vertical chamber without taking any precautions as to intermixing with the ascending and descending fraction, and flow patterns B, C and D correspond to those illustrated in Figures 3, 4 and 5, respectively. For all four flow patterns, the following conditions were equal:

The results at three different rates of feed are tabulated immediately below:

Difference in Refractive Viscqsity Index of Top Index between Ph and Feed Rate, Ps 1o4 Product (Ph) ml./hour A i B C i D A I B I C D It is apparent from the foregoing table that the methodl tion. All such modifications are intended to come within the scope of the invention as defined in the accompanying claims. v

I claim:

1. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow separation chamber having substantially smooth walls and two outer ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a first fraction adjacent one wall and another of said dissimilar components in a second fraction adjacent the other wall; circulating said first and second fractions countercurrently and endwise within the chamber; continuously withdrawing, from one outer end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the other' outer end of the chamber, a liquid product enriched in another of said dissimilar components; temporarily separating the first and second fractions from one another at a location intermediate the outer ends of the chamber; and continuously introducing fresh liquid mixture into at least one of the fractions while they are separated.

2.- A method vfor continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow separation chamber having substantially two outer ends; imposing a temperature Vgradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a first fraction adjacent one wall and another of said dissimilar components in a second fraction adjacent the other wall; circulating said first and second fractions countercurrently and endwise within the chamber; continuously withdrawing, from one outer end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the other outer end of the chamber, a liquid product enriched in another of said dissimilar components; temporarily separating the first and second fractions from one another at a location intermediate the outer ends of the chamber; and continuously admixing fresh mixture with at least one of said temporarily separated fractions.

3. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow separation chamber having substantially smooth walls and two outer ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture smooth walls and Y in a first fraction adjacent one wall and another of said dissimilar components in a second fraction adjacent the other wall; circulating said first and second fractions countercurrently and endwise within the chamber; continuously withdrawing, from one outer end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the other outer end of the chamber, a liquid product enriched in another of said dissimilar components; temporarily separating the first and second fractions from one another at a location intermediate the outer ends of the chamber; and continuously replacing one of said temporarily separated fractions with fresh liquid mixture.

4. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a fraction ascending adjacent the wall maintained at the higher ternperature and another of said dissimilar components in a fraction descending adjacent the other wall; continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fractions from one another at a location intermediate the upper and lower ends of the chamber; and continuously introducing fresh liquid mixture into at least one of the ascending and descending fractions while they are separated.

5. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a fraction ascending adjacent the wall maintained at the higher temperature and another of said dissimilar components in a fraction descending adjacent the other wall; continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fractions from one another at a location intermediate the upper and lower ends of the chamber; and continuously admixing fresh liquid mixture with at least one of the temporarily separated ascending and descending fractions.

6. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar cornponents that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture 'in a fraction ascending adjacent the wall maintained at the higher temperature and another of said dissimilar components in a fraction descending adjacent the other wall; continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fractions from one another at a location intermediate the upper and lower ends of the chamber; and continuously admixing fresh liquid mixture with the temporarily separated ascending fraction.

7. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a fraction ascending adjacent the wall maintained at the higher temperature and another of said dissimilar components in a fraction descending adjacent the other wall; continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fractions from one another at a location intermediate the upper and lower ends of the chamber; and continuously admixing fresh liquid mixture with the temporarily separated descending fraction.

8. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a fraction ascending adjacent the wall maintained at the higher temperature and another of said dissimilar components in a fraction descending adjacent the other wall; continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fractions from one another at a location intermediate the upper and lower ends of the chamber; and continuously admixing fresh liquid mixture with both temporarily separated fractions.

9. A method for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, which comprises confining the liquid mixture in a uniformly narrow and substantially vertical separation chamber having substantially vertical and smooth walls and upper and lower ends; imposing a temperature gradient across the liquid by maintaining one wall at a temperature higher than the temperature of the other wall, thereby concentrating one of said dissimilar components in the mixture in a fraction ascending adjacent the wall maintained at the higher temperature and another of said dissimilar components in a fraction descending adjacent the other wall;

continuously withdrawing, from the upper end of the chamber, a liquid product enriched in one of the dissimilar components; continuously withdrawing, from the lower end of the chamber, a liquid product enriched in another of said dissimilar components; continuously separating the ascending and descending fraction from one another at a location intermediate the upper and lower ends of the chamber; and continuously replacing one of said temporarily separated ascending and descending fractions With fresh Iliquid mixture.

l0. Apparatus for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the condition of separation, said apparatus comprising two wall surfaces closely and substantially uniformly spaced apart to form a thermal diffusion separation chamber having two outer ends, an inlet adjacent one of the wall surfaces land intermediate said |outer ends for introducing liquid mixture into the chamber, means for relatively heating and cooling the opposed wall surfaces for separating the liquid introduced into the chamber into a rst fraction enriched in one of said dissimilar components and moving toward one outer end of the chamber adjacent said one of the wall surfaces and a second fraction enriched in another of the dissimilar components and moving toward the other outer end of the chamber adjacent the other of the wall surfaces, an outlet for liquid at each outer end of the chamber, means intermediate the outer ends for separating the first and second fractions and means for directing the liquid introduced through the inlet into only the first separated fraction.

ll. Apparatus for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, said apparatus comprising two Wall surfaces closely and substantially uniformly spaced apart to form Ia thermal diffusion separation chamber having two outer ends, an inlet adjacent one of the wall surfaces land intermediate said outer ends for introducing liquid mixture into the chamber, means for relatively heating and cooling the opposed wall surfaces for separating the liquid introduced into the chamber into a rst fraction enriched in one of said dissimilar components and moving toward one outer end of the chamber adjacent said one of the wall surfaces and a second fraction enriched in another of the dissimilar components and moving toward the other outer end of the chamber adjacent the other of the wall surfaces, an outlet for liquid at each outer end of the chamber, means intermediate the 4outer ends for separating the iirst and second fractions and means for admixing the liquid introduced through the inlet with only the first separated fraction.

l2. Apparatus for continuously separating, by thermal diiusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, said apparatus comprising two wall surfaces closely and substantially uniformly spaced apart to form -a thermal diffusion separation chamber having two outer ends, lirst and second inlets intermediate said outer ends, one adjacent each wall surface, for introducing liquid mixture into the chamber, means for relatively heating and cooling the opposed wall surfaces for sepa-rating the liquid introduced into the chamber into a irst fraction enriched in one of said dissimilar components and moving toward one outer end of the chamber adjacent one of the w-all surfaces and a second fraction enriched in another of the dissimilar components and moving toward the other outer end of the chamber adjacent the other of the wall surfaces, an outlet for liquid product at each outer end of the chamber,

10 means intermediate the outer ends for separating the first and second fractions, means for direct-ing the liquid introduced through the rst inlet into only Ithe first separated fraction, and means for directing the liquid introduced through the second inlet into only 4the second separated fraction.

13. Apparatus for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, said apparatus comprising two wall surfaces closely and substantially uniformly spaced apart to form la thermal diffusion separation chamber having two outer ends, irst and second inlets intermediate said outer ends, one adjacent each wall surface, for introducing liquid mixture into the chamber, means for relatively heating and cooling the opposed wall surfaces for separating the liquid introduced into the chamber into a lirst fraction enriched in one of said dissimilar components and moving toward one outer end of the chamber adjacent 'one of the wall surfaces and a second fraction enriched in another of the dissimilar components and moving toward the other outer end of the chamber adjacent the other |of the wall surfaces, an outlet for liquid product at each outer end of the chamber, means intermediate the outer ends for separating the first and second fractions, means for admixing the liquid introduced through the first inlet with only the first separated fraction, and means for admixing the liquid introduced through the second inlet with only the second separated fraction.

14. Apparatus for continuously separating, by thermal ditfusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, said apparatus comprising two vertical wall surfaces closely and substantially uniformly spaced apart to form a vertical thermal diffusion separation chamber having upper and lower ends, an inlet adjacent one of the wall surfaces and intermediate said upper and lower ends for introducing liquid mixture into the chamber, means for relatively heating and cooling the opposed wall surfaces for separating the liquid introduced into the chamber into a rst fraction enriched in one of said dissimilar components and ascending toward the upper end of the chamber adjacent one of the Wall surfaces and a second fraction enriched in another of the dissimilar components and descending toward the lower end of the chamber adjacent the other of the wall surfaces, an outlet for liquid at each of the upper and lower ends of the chamber, means intermediate the upper and lower ends for separating the ascending and descending fractions and means for admixing :the liquid introduced through the inlet with only one of the separated fractions.

l5. Apparatus for continuously separating, by thermal diffusion, two liquid products containing dissimilar components that are normally liquid under the conditions of separation and which are included in a mixture normally liquid under the conditions of separation, said apparatus comprising iirst and second smooth, substantially parallel and vertical wall surfaces closely and substantially uniformly spaced apart to form a vertical thermal diffusion separation chamber having upper and lower ends, lirst and second inlets intermediate said upper and lower ends, one adjacent each of said rst and second wall surfaces, respectively, for introducing liquid mixture into the chamber, means for relatively heating and cooling the first and second wall surfaces, respectively, for separating the liquid introduced into the chamber into a first fraction enriched in one of said dissimilar components and ascending toward the upper end of the chamber adjacent Ithe iirst wall surface and a second fraction enriched in another of the dissimilar components and descending toward the lower end of the chamber adjacent the second wall surface, an outlet for liquid at each of the upper and lower ends of the chamber, means intermediate the upper and lower ends for separating the ascending and descending fractions, means -for admixing the liquid introduced through the rst inlet with only the ascending fraction and means for admixing the liquid introduced through the second inlet with only the descending fraction.

References Cited in the le of this patent UNITED STATES PATENTS McNitt Dec. 4, 1945 Beams Sept. 5, 1950 Jones etal Feb. 13, 1951 Jones et al Feb. 13, 1951 Hanson Feb. 12, 1952 

